The object of the proposed research is to study the regulatory functions of the surface membranes of mammalian cells, specifically nerve and muscle cells. The biochemical, electrophysiological and pharmacological properties of myoblasts and neuroblasts will be studied in cell cultures. Efforts will be directed towards the correlation of these three types of observations with cell cycle and cellular differentiation. Mutagens will be used in an effort to isolate genetic mutations which affect the systems under study, and myoblasts will be isolated from pure strains of mice which bear genetic mutations that alter muscle differentiation. The various cell lines will be cloned whenever possible, and fusion experiments will be performed in order to study the membrane properties of the hybrid cells.